1. Field of the Invention
The present invention relates to cutting tools, such as are used to machine a workpiece being turned on a lathe, in which one or more cutting surfaces of a cutting implement must be rotationally indexed. The invention is particularly well adapted to the indexing of cutting bits having a number of cutting surfaces which are to be successively brought into a cutting position with respect to a holder or housing which mounts the bit. Such indexing may be necessary, for example, to present a new cutting surface to the work when one has become worn.
In the past, such indexing has been performed manually. In particular, when one cutting surface of a bit has been used as desired, the machining operation is temporarily suspended while the bit is loosened on the holder, turned to present a new cutting surface to the work, and then re-tightened on the holder. This requires expensive loss of operating time. Additionally, it is inconvenient and even dangerous for the personnel who handle the bit since the latter becomes quite hot during use. Accordingly, there has been a need for a mechanism for automatically rotationally indexing a cutting implement, especially for indexing a cutting bit having a plurality of cutting surfaces so as to successively bring these surfaces into cutting position.
2. Description of the Prior Art
U.S. Pat. No. 3,838,500 to Wirfelt discloses a bit holder in which a new cutting surface is provided by completely ejecting the used bit and bringing a new one into place from a storage magazine.
U.S. Pat. No. 3,182,534 to Hoffman discloses a manually indexable bit in which a disc-like cutter is clamped in place between two plates. To change the cutting surface, a screw is loosened, one of the clamping plates is retracted slightly, and the cutter is manually rotated and then re-clamped.
U.S. Pat. Nos. 3,449,990 to Harman and 3,461,525 to Courley both disclose turret assemblies for indexing a tool holder so as to bring different bits into cutting position or to change the orientation of a bit. Each of these devices is quite complicated and involves a number of relatively moving parts. To effect the indexing, in either of the two devices, an actuating handle must be moved arcuately.